The primary purpose of this project is to identify and assess the relative importance of risk factors for coronary heart disease and stroke in an elderly population. Blood components previously identified as risk factors for cardiovascular disease in younger populations will be evaluated in an elderly population for their associations with both subclinical disease (as determined by Holter monitoring, echocardiography and ultrasound examination of the carotid arterial system) and with clinical disease (development of angina pectoris, coronary insufficiency, myocardial infarction and sudden death). The primary objective of the Central Blood Analysis Laboratory is to develop and implement procedures to measure these risk factors, and to monitor performance of a protocol for their measurement in the blood of subjects within the elderly study. The secondary objectives of the Central Blood Analysis Laboratory are to: 1) to develop a Manual of Operations for Field Center technical staff involved in sample acquisition and processing and to develop a Manual of Operations for the CBAL staff to perform the selected determinations, 2) to standardize and maintain quality control for methods to obtain, process, ship, store and measure concentrations or activities of blood components from multiple sites, and 3) to provide advice to the Project Steering Committee and NHLBI regarding the most useful selection of laboratory tests 4) to assist in data analysis and preparation of study reports.